Generally speaking, these phrases are, ahem, "best used" to describe how long a product will maintain its optimum quality (although "Sell By" indicates how long an establishment can sell perishable products). With that said, just because that carton of milk says "Sell By May 20" does not mean you should chug a glass when you see it's still in your fridge come August.

So now that you know, why not make up that shopping list and pick a dozen eggs without any worry. We bet that Denver omelet you're dying to make will have never tasted so good.